Overlaps is an option to StringCases, StringCount, and StringPosition that specifies how to treat overlapping substrings.
Overscript[x, y] is an object that formats as OverscriptBox[x, y].
PadRight[list, n] makes a list of length n by padding list with zeros on the right. PadRight[list, n, x] pads by repeating the element x. PadRight[list, n, {x_1, x_2, ...}] ...
ParallelArray[f, n] generates in parallel a list of length n, with elements f[i], evaluated.ParallelArray[f, {n_1, n_2, ...}] generates in parallel an n_1*n_2*... array of ...
PlayRange is an option for Play and related functions which specifies what range of sound amplitude levels should be included.
PolynomialQ[expr, var] yields True if expr is a polynomial in var, and yields False otherwise. PolynomialQ[expr, {var_1, ...}] tests whether expr is a polynomial in the var_i.
PositiveDefiniteMatrixQ[m] tests whether m is a positive definite matrix.
PrecedenceForm[expr, prec] prints with expr parenthesized as it would be if it contained an operator with precedence prec.
ReadProtected is an attribute that prevents values associated with a symbol from being seen.
RecordLists is an option for ReadList that specifies whether objects from separate records should be returned in separate sublists.